Within the interiors of their housings, modem personal computers are customarily provided with sheet metal cage structures adapted to receive and removably support a plurality of option or expansion cards which, when operatively installed in their associated cage structure, upgrade the operating capabilities of the computer. These expansion cards may be installed in the computer during its original manufacture or subsequently installed by the computer purchaser. Typical types of expansion cards include network, sound, graphics accelerator and multi-media cards.
An expansion card is basically a relatively small rectangular printed circuit board having, along one side edge, a connector edge portion that plugs into a corresponding socket portion of the cage structure to operatively couple the installed card to the motherboard or system planar of the computer. The socket portions of the cage structure are relatively oriented in a manner such that the expansion cards installed therein are arranged in a spaced apart, parallel, facing series with end edges of the cards being aligned with one another.
Extending along these aligned end edge portions of the expansion cards are sheet metal connecting brackets having outwardly bent securement tab portions positioned adjacent the side edge portions of the cards opposite their connector edge portions. These tab portions rest upon an inturned side wall ledge of the cage structure and have notches formed therein that overlie and register with a spaced series of threaded circular openings in the ledge. Each bracket tab is removably secured to the ledge by a screw that extends through the tab notch and is threaded into its associated ledge opening. This individual securement of the bracket tabs to the cage structure ledge serves to anchor the installed expansion cards in place within the cage structure, thereby preventing the connector edge portions of the cards from being dislodged from their associated connector sockets during shipping and handling of the computer.
This conventional use of individual screws to removably secure the card bracket tabs to the cage structure carries with it several well known disadvantages. For example, during initial installation of the expansion cards within the cage structure one or more of the retaining screws can easily fall into the typically crowded interior of the computer, thereby creating what may be a difficult retrieval problem. Additionally, when a series of expansion cards are installed at the factory each individual bracket retaining screw is typically installed using an automated assembly machine. Several seconds are required to install each screw, thereby appreciably increasing the overall assembly time for each computer in which expansion cards are to be factory installed.
The use of individual card bracket tab retaining screws also creates potential problems and inconveniences for the purchaser of the computer or technicians that subsequently work on the expansion card portion of the computer. For example, when subsequently adding or exchanging expansion cards, the technician or computer owner must unscrew the bracket tab in place and then reinsert the removed screw into the bracket tab of the added expansion card. Often, more than one card must be dealt with. This, of course, requires that multiple screws must be removed and then be reinserted. Each fine this task is carried out, there is the potential for dropping one or more of the individual retaining screws into the computer system. Additionally, when the computer system is being analyzed for a problem, it is often necessary to remove all of the expansion cards to isolate the problem. This requires the technician or computer owner to remove and reinstall all of the individual retaining screws (a process that may have to be repeated several fines during the problem analysis process), thereby further increasing the possibility that one or more screws will be dropped into the interior of the computer system.
To deal with the inconvenience posed by the above discussed conventional attachment system, a system that uses a single bar laid across the top flanges of all of the brackets held down by a single screw has been developed, such as the device disclosed in U.S. Pat. No. 5,317,483 which is incorporated herein by reference. The device disclosed in U.S. Pat. No. 5,317,483 is a substantial improvement over other prior art devices in that it eliminates the plurality of screws involved in the conventional systems. With only one screw being present, only one screw must be removed to remove one or more of the brackets. This, of course, reduces the amount of time spent in the manufacturing process to attach the blank brackets or expansion cards and also decreases the amount of aggravation for the computer user who adds or removes additional expansion cards or blanket brackets after the purchase of the computer. While this system has certainly improved the conventional problem of dealing with a multiplicity of screws it does not address fully the problem which remains; that is the problem associated with the fact that when the cross bar is removed the blank brackets have very little support to stay in their proper position. As such, they have a tendency to fall off during the manufacturing process and during the repair or expansion operations.
Other devices similar to the device disclosed in U.S. Pat. No. 5,317,483 are also known. These other devices also include an elongated bar having gripping members extending perpendicularly from the opposite ends of the elongated bar to form a "U" shape. The device is hinged via bent tabs extending from the back of the device through openings formed in the computer chassis wall. The elongated bar member lays across one or more card guides that have been positioned on the upper ledge of the card cage, and the gripping members engage openings in the side edges of the card cage to hold the card guides about the card cage. While this device eliminates the use of screws completely, it too suffers from the disadvantages. For example, two hands must be used to simultaneously disengage the gripping members from the openings. Additionally, once the bar is removed, all of the card guides are susceptible to falling off. This is particularly true where the card guides are blank card guides.
Accordingly, there is a need in the art for an improved apparatus for removably retaining expansion cards in an associated support cage structure in order to eliminate or at least substantially minimize the above-mentioned problems associated with the conventional use of individual card bracket tab retaining screws and cross bars. The present invention address these needs.